Some days I can play great D without fouling, hitting all ball and some days it feels like i foul my man on every drive. Anyone have any tips on how to avoid fouls without taking to much away from tough defense?

Keep your arms straight (know when to block but otherwise try to obstruct their view) and make sure you do warmups before a game to keep your feet quick. Not much else to it IMO.

Stay in front of your man and adjust fast, gotta know where your man's feet are and where yours are. Don't focus so much on blocking, a lot of days it can be a waste of time because you'll be grazing their arm just enough. Only block when you 'feel' it.

make it a habit to move your feet and when a guy runs into you be ready to make contact. i dont man bump him with your hips, I mean make quick shuffles to beat the guy to the spot and take the contact in the middle of your chest. that way if he spins or crosses over he'll still be within range of recovery/making a good defensive play when he goes to shoot